Comparison of the Intraocular Pressure Measured Using the New Rebound Tonometer Icare ic100 and Icare TA01i or Goldmann Applanation Tonometer:

A comparison of intraocular pressure measurement using SUOER SW-500 rebound tonometer and conventional reusable Goldmann prisms

Introduction

To determine the agreement between intraocular pressure (IOP) measurements using conventional Goldmann applanation tonometry (GA1,2T) and SUOER SW-500 Rebound Tonometer.

Methods

This was a retrospective observational study where 205 eyes of 106 glaucoma patients had their IOPs measured by 2 fellowship trained ophthalmologists. Data were analyzed using the Bland-Altman method of differences. Correlation was measured using the Pearson coefficient.

Results

Most of our patients were Chinese (88.7%) and female (51.9%). The average age was 66.9 years. The range of IOPs as measured by GAT was 2 to 58 mm Hg. Using the Bland-Altman method to compare GAT and SUOER SW-500 Rebound Tonometer. The tonometer overestimated the IOP by 0.5 mm Hg in the right eye and underestimated it by 0.1 mm Hg in the left eye. Overall, the tonometer overestimated the IOP by 0.2 mmHg. The Tonometer IOP correlated well with GAT, with a Pearson coefficient of correlation(r) of 0.89 (p < 0.001) for the right eye and 0.86 (p < 0.001) for the left eye, respectively. In patients with GAT IOP ≥ 21 mm Hg (n = 25), the Tonometer underestimated the IOP by 2.96 mm Hg.

Discussion

The IOP measurements from the SUOER SW-500 Rebound Tonometer correlates well with the conventional GAT in measuring the IOP within normal ranges of IOP. SUOER SW-500 Rebound Tonometer may be of use, especially if the risk of transmission of infection is high considering that the probes are disposable. It is easy to use and its small size and portability makes it useful in situations where the patient is unable to be examined at the slit lamp.

Nicotinamide Prevents Retinal Vascular Dropout in a Rat Model of Ocular Hypertension and Supports Ocular Blood Supply in Glaucoma Patients

Purpose

To investigate whether nicotinamide (NAM) modulates retinal vasculature in glaucoma.

Methods

This was a prospective controlled clinical trial investigating animal and human histopathology. Participants included normotensive and ocular hypertensive rats, postmortem human ocular tissue, glaucoma patients (n = 90), and healthy controls (n = 30). The study utilized histopathology, computer-assisted retinal vasculature analysis, optical coherence tomography angiography (OCTA), and NAM treatment. The main outcome measures included retinal vascular parameters in rats as assessed by AngioTool; retinal vasculature integrity in rats and humans as assessed by histopathology, antibody-staining, and ImageJ-based measurements; and retinal perfusion density (PD) and flux index in humans as assessed by OCTA.

Results

A number of vessel parameters were altered in ocular hypertension/glaucoma compared to healthy controls. NAM treatment improved the retinal vasculature in ocular hypertensive rats, with an increase in mean vessel area, percentage area covered by vessels, total vessel length, total junctions, and junction density as assessed by AngioTool (all P < 0.05); vessel wall integrity as assessed by VE-cadherin antibody staining was also improved (P < 0.01). In humans, as assessed by OCTA, increases in PD in the optic nerve head and macula complete image (0.7%, P = 0.04 and 1.0%, P = 0.002, respectively) in healthy controls, and an increase in the temporal quadrant of the macula (0.7%, P = 0.02) in glaucoma patients was seen after NAM treatment.

Conclusions

NAM can prevent retinal vascular damage in an animal model of glaucoma. After NAM treatment, glaucoma patients and healthy controls demonstrated a small increase in retinal vessel parameters as assessed by OCTA.

Comparison of intraocular pressure measured by iCare tonometers and Goldmann applanation tonometer

OBJECTIVE

To evaluate the relationship between the Goldmann applanation tonometer (GAT) and the iCare PRO and iCare IC200 tonometers in measuring intraocular pressure (IOP) in adult eyes with a diagnosis of glaucoma or glaucoma suspect.

PARTICIPANTS AND METHODS

One hundred and one eyes from 101 participants diagnosed with glaucoma or glaucoma suspect were evaluated in this study. IOP was measured by iCare PRO and iCare IC200 tonometers in a randomized sequence followed by IOP measurements by the GAT tonometer and then central corneal thickness measurements. After the IOP measurements, participants scored their comfort level using a visual analog scale with each tonometer. Intraclass correlation coefficient (ICC) and Bland-Altman analysis were used to investigate the agreement among tonometers. SPSS and Microsoft Excel programs were used for statistical analysis.

RESULTS

Overall, there was good agreement among the 3 tonometers used in this study. The ICC for the iCare PRO and the iCare IC200 was 0.95 (p < 0.001), and the ICC for the iCare PRO and the GAT and the iCare IC200 and the GAT was >0.80 (p < 0.001). However, both iCare tonometers underestimated IOP by approximately 2 mm Hg compared with the GAT. Furthermore, 84% of iCare readings fall within ±5 mm Hg of GAT measurements. Neither body mass index nor central corneal thickness affected the IOP agreement among the tonometers. Participant response on visual analog scale rated IOP measurements by iCare tonometers to be more comfortable than the GAT.

CONCLUSION

Our results demonstrated a good agreement between iCare tonometers and GAT; but iCare tonometers underestimated IOP compared to the GAT.

Analysis of the influence of corneal properties and densitometry on applanation and rebound tonometry in primary open angle glaucoma

PURPOSE

To evaluate the influence of corneal densitometry on portable applanation (Perkins) and rebound (iCare ic100 and PRO) tonometry. A secondary goal was to assess if there was a relationship between various corneal properties and the severity of primary open angle glaucoma (POAG).

MATERIAL AND METHODS

Seventy-five eyes of 75 patients with primary open angle glaucoma were studied, divided by severity into 3 groups: 25 mild, 25 moderate and 25 advanced. Intraocular pressure (IOP) was measured 3 times in each participant with a Perkins applanation tonometer (PAT), a handheld version of the Goldman applanation tonometer (GAT), an iCare PRO and an iCare ic100. Mean values were then calculated. Corneal topography with the Pentacam HR (Oculus, Wetzlar, Germany) was also performed in all individuals.

RESULTS

Mean age and sex were comparable in all groups, as were densitometry values (P>0.05). The mean visual field defect (MD) was 2.85 (±1.23) dB in the mild glaucoma group, 8.26 (±1.90) dB in the moderate group and 15.66 (±3.46) dB in the advanced group. Three multivariate regression analyses were performed. The first and second calculations assessed the effect of IOP obtained with iCare ic100 and PAT as dependent variables with age, sex, CCT and mean keratometry (Km) within the glaucoma subgroups and the global sample. The third analysis was carried out to assess the relationship between corneal densitometry as the dependant variable and the aforementioned corneal parameters among the glaucoma groups. In the first multivariate regression analysis, a statistically significant correlation was found between ic100 rebound tonometry and CCT in the POAG global sample (coef. 0.117; IC [-0.21-(-0.01)]; P=0.025). No statistically significant correlation was found in the subgroup analyses. In the second multivariate analysis, no significant correlation was found between PAT and CCT, Km, age or sex (P>0.05). In the third analysis, densitometry was correlated with age in all glaucoma subgroups (P<0.001) and with CCT in the moderate glaucoma subgroup (coef. -0.037; IC [-0.67-(-0.01)]; P=0.021). Tonometry appeared to be minimally influenced by corneal densitometry, with a mild positive linear correlation seen (R=0.03). IOP values were similar with 3 of the tonometers: PAT 16.07 (±3.18) mmHg, PRO 16.27 (±3.42) mmHg and ic100 15.17 (±4.28) mmHg. There was, however, a significant underestimation of IOP with ic100 (-0.89mmHg) compared to PAT (P=0.007).

CONCLUSION

Corneal densitometry did not show significant differences between glaucoma severity groups. A positive correlation was seen with CCT and both corneal densitometry and age. No correlation was found with keratometry or severity of glaucoma. The influence of corneal densitometry on IOP measurements appears weak, with little clinical relevance identified.

Different Effects of Aging on Intraocular Pressures Measured by Three Different Tonometers

This study aimed to compare intraocular pressures (IOP) using different tonometers, Goldmann applanation (IOP_GAT), non-contact (IOP_NCT), and rebound (IOP_RBT), and to assess the effects of aging and central corneal thickness (CCT) on the measurements. The IOP_GAT, IOP_NCT, IOP_RBT, mean patient age (65.1 ± 16.2 years), and CCT (521.7 ± 39.2 µm) were collected retrospectively from 1054 eyes. The differences among IOPs were compared by the paired t-test. Possible correlations between devices, age, and CCT were assessed by linear regression analyses. The effects of age and CCT on the IOP reading were assessed by mixed-effects regression models. The IOP_GAT values were 2.4 and 1.4 mmHg higher than IOP_NCT and IOP_RBT, respectively; the IOP_NCT was 1.0 mmHg lower than IOP_RBT (p < 0.0001 for all comparisons). The IOPs measured by each tonometer were highly correlated with each other (r = 0.81–0.90, t = 45.2–65.5). The linear regression analyses showed that age was negatively correlated with IOP_NCT (r = −0.12, t = −4.0) and IOP_RBT (r = −0.14, t = −4.5) but not IOP_GAT (r = 0.00, t = −0.2); the CCT was positively correlated with IOP_GAT (r = 0.13, t = 4.3), IOP_NCT (r = 0.29, t = 9.8), and IOP_RBT (r = 0.22, t = 7.2). The mixed-effect regression models showed significant negative correlations between age and IOP_NCT (t = −2.6) and IOP_RBT (t = −3.4), no correlation between age and IOP_GAT (t = 0.2), and a significant positive correlation between CCT and the tonometers (t = 3.4–7.3). No differences between IOP_GAT and IOP_RBT were seen at the age of 38.8 years. CCT affects IOPs from all tonometers; age affects IOP_NCT and IOP_RBT in different degrees. IOP_RBT tended to be higher than IOP_GAT in young subjects, but this stabilized in middle age and became higher in older subjects.

Agreement between rebound (Icare ic200) and applanation tonometry (Perkins) in patients with primary congenital glaucoma

PURPOSE

To examine agreement between intraocular pressure (IOP) measurements made using the rebound tonometer Icare ic200 (RT200) and the Perkins handheld applanation tonometer (PAT) in patients with primary congenital glaucoma (PCG). The impacts of several covariables on measurements using the two devices were also assessed.

MATERIALS AND METHODS

Intraocular pressure measurements were made in a single session in 86 eyes of 86 patients with PCG (46 under anaesthesia, 40 in the office). The order was RT200 then PAT. The variables age, central corneal thickness (CCT), corneal state and anaesthesia were recorded in each patient. Data were compared by determining interclass correlation coefficients (ICC) for each tonometer and representing the differences detected as Bland-Altman plots. Effects of covariables were assessed through univariate and multivariate regression.

RESULTS

Mean IOP difference between tonometers (RT200 minus PAT) was 1.26 mmHg (95%: 0.22-2.31). Absolute agreement (ICC) was 0.73 (95% CI: 0.62-0.82). Lower and upper limits of agreement (95%) were -8.06 mmHg (95% CI: -9.87 to -6.25) and 10.59 mmHg (95% CI: 8.77-12.40), respectively. The tonometers showed systematic differences (a = -4.63 mmHg; 95% CI: -9.11 to -1.44) and proportional differences; for each mmHg increase in PAT-IOP, the RT200 reading increased by 1.28 mmHg (b = 1.28; 95% CI: 1.12-1.53). None of the variables tested as predictors were able to explain differences between the tonometers.

CONCLUSIONS

Despite the good overall agreement between both tonometers, caution should be taken in high values of IOP, considering the interchangeability of its readings as systematic and proportional differences appear to exist between both methods.

How to Measure Intraocular Pressure: An Updated Review of Various Tonometers

Intraocular pressure (IOP) is an important measurement that needs to be taken during ophthalmic examinations, especially in ocular hypertension subjects, glaucoma patients and in patients with risk factors for developing glaucoma. The gold standard technique in measuring IOP is still Goldmann applanation tonometry (GAT); however, this procedure requires local anesthetics, can be difficult in patients with scarce compliance, surgical patients and children, and is influenced by several corneal parameters. Numerous tonometers have been proposed in the past to address the problems related to GAT. The authors review the various devices currently in use for the measurement of intraocular pressure (IOP), highlighting the main advantages and limits of the various tools. The continuous monitoring of IOP, which is still under evaluation, will be an important step for a more complete and reliable management of patients affected by glaucoma.

A Review to Populate A Proposed Cost-Effectiveness Analysis of Glaucoma Screening in Sub-Saharan Africa

To populate a proposed cost-effectiveness analysis of glaucoma screening in Sub-Saharan Africa (SSA).A complete search was conducted on PubMed, Medline and African Journals Online (AJOL) to obtain relevant published articles, which were included in this review. All relevant articles on prevalence of glaucoma in SSA and among other African-derived populations, severity of glaucoma, cost of diagnosis and management, clinical effectiveness of glaucoma screening and treatment and the different glaucoma screening strategies in SSA were reviewed.Population screening interventions for glaucoma may be considered as follows: standalone screening for glaucoma, screening for glaucoma during cataract outreach, and screening incorporated with diabetic retinopathy image review using tele-ophthalmology. Our review suggests that cost of glaucoma treatment is relatively low with cost of medical treatment ranging from USD 273 to USD 480 per year/patient and surgical treatment cost of USD 283 per patient as with other developing countries. Compliance with medication is moderate to good in about 50% of glaucoma patients. Prevalence of glaucoma is much higher in SSA and almost 50% of glaucoma patients are blind in at least one eye at presentation in clinics (without outreach screening). Our review suggests a moderate sensitivity and specificity in identifying glaucoma with basic equipment (direct ophthalmoscope, contact tonometer and frequency doubling technology) during outreach screening although about a third or fewer take up glaucoma services in clinics.Our review provides the necessary information to conduct a cost-effective analysis of glaucoma screening in SSA using the decision Markov model.

Telehealth and Screening Strategies in the Diagnosis and Management of Glaucoma

Telehealth has become a viable option for glaucoma screening and glaucoma monitoring due to advances in technology. The ability to measure intraocular pressure without an anesthetic and to take optic nerve photographs without pharmacologic pupillary dilation using portable equipment have allowed glaucoma screening programs to generate enough data for assessment. At home, patients can perform visual acuity testing, web-based visual field testing, rebound tonometry, and video visits with the physician to monitor for glaucomatous progression. Artificial intelligence will enhance the accuracy of data interpretation and inspire confidence in popularizing telehealth for glaucoma.

Evaluation of rebound tonometer iCare IC200 as compared with IcarePRO and Goldmann applanation tonometer in patients with glaucoma

Background

This study investigated the agreement between a new rebound tonometer, IC200, and IcarePRO and Goldmann applanation tonometry (GAT).

Methods

This was a prospective cross-sectional study. We measured the intraocular pressure (IOP) in 145 eyes of 145 glaucoma patients in the sitting position using GAT, IcarePRO, and IC200. IcarePRO and IC200 measurements were also obtained in the supine position. IC200 measurement was performed using two modes: single six (IC200-single) and automatic (IC200-continuous) six-measurements mode.

Results

All tonometers provided high reproducibility in both positions (all intraclass correlation coefficients > 0.90), although it was highest with GAT, followed by IC200-continuous and IC200-single and then IcarePRO. In the sitting position, the mean (± SD) IOPs of GAT, IcarePRO, IC200-single, and IC200-continuous were 14.5 ± 2.9 mmHg, 13.3 ± 3.2 mmHg, 11.6 ± 3.2 mmHg, and 11.5 ± 3.2 mmHg, respectively. IOPs measured with IcarePRO or IC200 were significantly lower than those with GAT, particularly in patients with low IOP. IOPs measured with all tonometers were significantly elevated in the supine position as compared with the sitting position, but this difference was significantly greater with IC200-single and IC200-continuous compared with IcarePRO. IOP elevation was significant in eyes without bleb versus those with bleb, but this finding was not observed when IOP was measured with IcarePRO. The IOPs of the single and continuous modes of IC200 were interchangeable in both positions.

Conclusions

GAT, IcarePRO, and IC200 had sufficiently high reproducibility, but measurements with IcarePRO may not be accurate in the supine position. Elevation of IOP in the supine position, especially in eyes with bleb, was more sensitively captured with IC200 than with IcarePRO.

Trial registration

Japan Clinical Trials Register, No. UMIN000039982.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00249-z.

Correlation of iCare ic100 tonometry with iCare TA01i in screening of unselected population in Northern Finland Birth Cohort Eye study

PURPOSE

iCare tonometers are easy-to-use and portable devices for measuring the intraocular pressure (IOP). Purpose was to evaluate the IOP values measured by both novel iCare ic100 and conventional model TA01i devices in unselected population.

METHODS

IOP was measured with iCare ic100 and TA01i tonometers in 149 participants aged 32-33 years (born in 1985 or 1986) of the Northern Finland Birth Cohort Eye 2 study. The right eye of each participant was selected for analysis. We also collected data on axial length, corneal curvature and central corneal thickness (CCT). Bland-Altman plot was used for comparing the values obtained by these devices.

RESULTS

Mean IOP measured with the ic100 device was 13.8 (3.4) mmHg, with TA01i it was 12.5 (3.0) mmHg. The mean difference between these devices was 1.30 mmHg (p < 0.001) and R2 was 0.694. In Bland-Altman analysis, the agreement between the two tonometers ic100 and TA01i was constantly good (mean difference -1.30, ic100 device showing higher measures). There was a correlation between IOP and CCT (r = 0.269, p < 0.001 for ic100 and r = 0.255, p = 0.002 for TA01i), but not with IOP and corneal curvature or IOP and axial length.

CONCLUSION

In summary, we found ic100 rebound tonometry to be both reliable and effective, although CCT may influence IOP measurements with ic100 and TA01i. Therefore, iCare ic100 is suitable for IOP measurement in large cohort studies.

Comparison of the Icare ic100 Rebound Tonometer and the Goldmann Applanation Tonometer in 1,000 Eyes

BACKGROUND

Measurement of intraocular pressure (IOP) forms a crucial component in the diagnosis and management of glaucoma. Many devices have been developed to measure IOP with Goldmann applanation tonometry (GAT) considered the gold standard for IOP measurement.

OBJECTIVES

The objective was to compare the IOP measured using Icare ic100 and GAT.

METHODS

This cross-sectional study measured IOP in 1,000 eyes (500 left and 500 right) using the Icare ic100 and GAT. Central corneal thickness (CCT) was measured using a hand-held pachymeter. IOP measurements were investigated in all eyes, by IOP substrata, by CCT group, by number of topical glaucoma medications, and diagnosis.

RESULTS

There was moderate agreement between ic100 and GAT IOP measurements (intraclass correlation coefficient 0.73). Mean IOP was significantly lower when measured by ic100 than by GAT (12.1 vs. 16.2 mm Hg, p < 0.0001). Mean ic100 IOPs were also significantly lower than mean GAT IOPs within each IOP strata ≤12 (7.9 vs. 9.7 mm Hg, p < 0.0001), 13-21 (12.1 vs. 16.6 mm Hg, p < 0.0001), and ≥22 (18.4 vs. 25.2 mm Hg, p < 0.0001) and within each subanalysis.

CONCLUSIONS

The Icare tonometer consistently under estimated IOP compared to GAT, irrespective of CCT ranges and other subgroup analyses. The mean difference of 4.2 mm Hg can have significant clinical implications, particularly in the management of glaucoma patients.

Comparision of intraocular pressure measured using the new icare 200™ rebound tonometer and the Perkins™ applanation tonometer in healthy subjects and in patients with primary congenital glaucoma

OBJECTIVE

To compare intraocular pressure (IOP) measurements obtained using the Icare 200™ (IC200) rebound tonometer and the hand-held version of the Goldmann Applanation Tonometer (Perkins™ tonometer, GAT) in patients with primary congenital glaucoma (PCG) and in healthy subjects.

MATERIAL AND METHODS

A total of 42 eyes of healthy subjects (G1) and 40 patients with PCG (G2) were analysed. The following clinical data were collected: gender, age, Cup/Disc ratio, central corneal thickness (CCT). IOP was determined in the examination room using the IC200 and GAT tonometers, in the same order. Agreement between both tonometers was determined using the intraclass correlation coefficient (ICC) and Bland-Altman plot. A linear regression analysis was used to establish the IOP was affected by the studied variables.

RESULTS

Mean IOP between both tonometers (IC200 minus GAT) was: G1=15.91 (2.57) mmHg vs. 15.06 (2.12) mmHg (mean difference, MD=0.84 (0.50) mmHg; P<.101) and G2=20.10 (6.37) vs.19.12 (5.62) (MD=0.98 (1.36); P=.474). Excellent agreement was found between IC200 and GAT in both groups (ICC=G1: 0.875 (95% CI; 0.768-0.933; P<.001); G2: 0.924 (95% CI; 0.852-0.961; P<.001), and there was a statistically significant correlation between the IOP difference measured with IC200 and GAT and CCT in G1 (B=0.021; 95% CI; 0.005-0.037; P=.008), but was not statistically significant in G2.

CONCLUSION

There was excellent agreement between the IC200 and GAT tonometers, both in healthy subjects and PCG, with a trend to overestimate IOP when measured with IC200. There was no influence by CCT on IOP measurements in patients with PGC.

Ophthalmic findings in 10 captive, anesthetized chimpanzees (Pan troglodytes)

OBJECTIVES

To document ophthalmic findings, Schirmer's tear test I (STT), and intraocular pressure (IOP) values for anesthetized chimpanzees (Pan troglodytes).

ANIMALS STUDIED

Ten captive chimpanzees from Zoo Knoxville and Chattanooga Zoo.

PROCEDURES

Ten chimpanzees were anesthetized for annual physical examinations, blood collection, and ophthalmic examination. Each was anesthetized with intramuscular (IM) injections of dexmedetomidine, midazolam, and ketamine. Ophthalmic findings and STT and IOP values in addition to general health information were recorded for each chimpanzee. Pupillary diameter was measured after topical tropicamide administration. A Shapiro-Wilk test of normality was done for age, weight, STT values, IOP values, and pupil size.

RESULTS

Ages ranged from 11 to 42 years. Weight range was 40.9-83.6 kg. The mean STT was 13.4 ± 5.3 mm/min. The mean IOP was 14 ± 4.2 mm Hg. Seven of the 10 chimpanzees were considered geriatric, and each had perilimbal lipid deposits. Sedative-associated miosis was successfully counteracted with a regimen of repeated applications of tropicamide, enabling complete fundic examination.

CONCLUSIONS

A complete ophthalmic examination can be done on anesthetized chimpanzees with the protocol used in this study.

Analysis of reproducibility, evaluation, and preference of the new iC100 rebound tonometer versus iCare PRO and Perkins portable applanation tonometry

Objectives:

To analyze the reproducibility of the new iC100 rebound tonometer, to compare its results with the applanation tonometry and iCare PRO and to evaluate the preference between them.

Materials and methods:

For the study of reproducibility, 15 eyes of 15 healthy Caucasian subjects were included. Three measurements were taken each day in three separate sessions. For the comparative study, 150 eyes of 150 Caucasian subjects were included (75 normal subjects and 75 patients with glaucoma). Three consecutive measurements were collected with each tonometer, randomizing the order of use. The discomfort caused by each tonometer was evaluated using the visual analogue scale.

Results:

No statistically significant differences were detected between sessions. In the comparison between tonometers, the measurements with iC100 were statistically lower than those of Perkins (−1.35 ± 0.417, p = 0.004) and that iCare PRO (−1.41 ± 0.417, p = 0.002). The difference between PRO and Perkins was not statistically significant ( p = 0.990). The mean time of measurement (in seconds) with iC100 was significantly lower than with Perkins (6.74 ± 1.46 vs 15.53 ± 2.01, p < 0.001) and that PRO (6.74 ± 1.46 vs 11.53 ± 1.85, p < 0.001). Visual analogue scale score with iC100 was lower than Perkins (1.33 ± 0.99 vs 1.73 ± 1.10, p < 0.05). In total, 61.7% preferred iC100 against Perkins.

Conclusion:

The reproducibility of this instrument has been proven good. iC100 underestimates intraocular pressure compared to applanation tonometry at normal values and tends to overestimate it in high intraocular pressure values. Most of the subjects preferred iC100 tonometer.